There are a variety of applications for integrated circuit packages having embedded sensors. The sensor may have a single pixel element or may be a matrix of pixel elements, which individually generate an electrical signal that is responsive to the intensity of received light.
In one category of applications, embedded sensors are used in electronic devices that employ optical navigation as a means for operation. For example, hand-held scanners and computer mice may include “optical navigation engines” to track movement along a surface. The engine may be contained within a single integrated circuit package and may include an image acquisition system and an image processor. In operation, the engine identifies texture or other features of the surface being imaged and generates navigation information on the basis of the imaged features. As one possibility, the sensor captures a succession of image frames and the processor identifies common features within two frames and determines the distance between the common features from the first frame to the second. Such information can then be translated into X and Y coordinates to indicate movement of a scanner, mouse or other device.
FIGS. 1 and 2 illustrate one possible embodiment of an assembly having navigation capability. An assembly of this type may be used in an optical mouse or a hand-held scanner. In FIG. 1, the assembly is shown as being in a position to image a surface of a substrate 10, such as a mouse pad or a desktop. FIG. 2 shows the assembly in an exploded view. The assembly includes an integrated circuit package, which may be referred to as the sensor 12 because it includes an embedded sensor die 14. The downwardly extending leads of the sensor are attached to a corresponding set of vias of a printed circuit board 16 to provide mechanical and electrical coupling of the sensor to the assembly. A light emitting diode (LED) 18 is also mechanically and electrically connected to the printed circuit board. Mechanical coupling, as well as optical coupling, can be enhanced by use of a plastic clip 20 to provide a light mechanical compression on the top of the sensor 12 and to properly seat the LED.
A single-piece lens system 22 includes both a prism feature and a collection feature. A pyramidal region 24 provides the prism feature, wherein light from the LED 18 is reflected first downwardly and then at the desired angle for illuminating the surface of the substrate 10. Light reflected from the surface is collected by a lens 26 and directed to the embedded sensor die 14. In FIG. 2, the lens 26 is located within an optical window 28.
The lens 26 includes a ring portion 30 that is dimensioned to correspond to a stepped area 32 of a base plate 34. In addition to the corresponding dimensions, the proper alignment of the lens system 22 to the base plate 34 is ensured by an alignment post 36 that extends through an opening 38 of the printed circuit board 16 and by a raised feature 40 that contacts the lens 26 (as best seen in FIG. 1).
The assembly of FIGS. 1 and 2 is merely one example of an approach for providing the precise alignment of the necessary components. While the known approaches operate well for their intended purposes, they involve exacting manufacturing tolerances and assembly procedures.